Spectral sensors for noninvasive measurement or calculation of physiologic parameters (PP) such as, for example, oxygen saturation, oxygen tension, pH, hematocrit, hemoglobin concentration, anaerobic threshold, water content, and oxygen consumption, which are described in the art, for example in U.S. Patent Application Publication No. 2011/0205535, published Aug. 25, 2011 (“the '535 Publication”), the contents of which are incorporated by reference herein in their entirety for all purposes. One such spectral sensor 10 is illustrated in FIGS. 1 and 2, reproduced from the '535 Publication, which show a spectral detector 12, two short-distance radiation sources 14a, 14b, and six long-distance radiation sources 16a-16e. The housing 11 includes a concave inner surface that is configured for placement against a patient's skin above tissue, for example peripheral muscle tissue, which is to be monitored. The housing 11 further includes a handle 15 on each side, as well as apertures 17a, 17b for communications interface. As shown in FIG. 2, the radiation sources 14a, 14b and 16a-16e may be part of a circuit board 18.
However, spectral sensors such as sensor 10 often rely in general on their initial positioning over a larger muscle, for example a shoulder or arm muscle, without any indication or assistance in positioning based upon effectiveness of tissue illumination.